The production of impregnations of building construction products utilizes resin dispersions which have hitherto generally consisted of aqueous resoles or acrylate dispersions. Dispersions based on resoles are thinnable with water, but eliminate formaldehyde on curing and hence fabrication can only be carried out in plant specifically designed for that purpose. Acrylate dispersions can be cured without emission of environmentally harmful substances, but the cured products have a low glass transition temperature and an unfavorable performance in fire.
Resins based on benzoxazines are known from the prior art. DE 23 23936, for instance, states that such compounds are obtainable by a reaction of phenols with primary amines and formaldehyde wherein either the phenols have at least two hydroxyl-substituted aromatic ring systems per molecule or the amines have at least two primary amino groups per molecule. Such resins have the particular advantage that they are crosslinkable without addition of further curing agents, which has the advantage of avoiding environmentally harmful elimination products which can escape. However, coating with resin dispersions based on benzoxazines does require a solvent, resulting in emission problems.
It is an object of the present invention to provide resin dispersions whose processing avoids the release of environmentally burdensome materials and at the same time gives rise to products having a high glass transition temperature.